Closed-cell tannin-based foams without formaldehyde

ABSTRACT

Disclosed are foam compositions and processes to form closed-cell tannin-based foams. The foams comprises a continuous polymeric phase defining a plurality of cells, wherein the continuous polymeric phase comprises a tannin-based resin derived from a tannin and a monomer, wherein the monomer comprises furfural, glyoxal, acetaldehyde, 5-hydroxymethylfurfural, acrolein, levulinate esters, sugars, 2,5-furandicarboxylic acid, 2,5-furandicarboxylic aldehyde, urea, difurfural (DFF), furfuryl alcohol, glycerol, sorbitol, lignin, or mixtures thereof, and wherein the plurality of cells comprises a plurality of open-cells and a plurality of closed-cells with an open-cell content measured according to ASTM D6226-5, of less than 50%. The foam composition also comprises a discontinuous phase disposed in at least a portion of the plurality of closed-cells, the discontinuous phase comprising one or more blowing agents.

This application claims benefit under 35 U.S.C. §119(e) of U.S.Provisional Patent Application Nos. 61/489,854; 61/489,787; 61/489,790;61/489,795; 61/489,803; and 61/489,847 filed on May 25, 2011, which areherein incorporated by reference.

FIELD OF THE INVENTION

This invention relates in general to tannin-based foams and inparticular to compositions and processes for producing closed-celltannin-based foams.

BACKGROUND INFORMATION

Due to depleting world energy resources and global warming, there is adrive to improve energy efficiency of new and existing commercial andresidential buildings. One of the strategies is to improve thermalinsulation around the buildings. Currently, the building industry usesseveral different forms of insulation materials, for example, glassfibers and mineral fibers. However, glass and mineral fibers exhibithigh thermal conductivity in the range of 0.03-0.04 W/m·K. Incomparison, aerogels exhibit thermal conductivity in the range of0.008-0.012 W/m·K, but aerogels are very fragile and lack the mechanicalstrength needed for thermal insulation for building applications.

Apart from fibrous insulation, certain types of polymeric foams arecommonly used for insulation applications that exhibit thermalconductivity in between those of glass fibers and aerogel materials.Only foams that are blown from low thermal conductivity blowing agentsand result in a predominantly closed cell structures, with significantfraction of the blowing agent trapped within the closed cells, canexhibit low thermal conductivity and high insulating values. Commercialfoams with high insulation value are blown from low temperature boilingliquids such as hydrocarbons and hydro fluorocarbons (HFCs), whichexhibit a gas phase thermal conductivity in the range of 0.008-0.015W/m·K. Therefore, the foams that result from such blowing agents canexhibit thermal conductivity in the range 0.018-0.030 W/m·K. However,some of the hydrocarbons and hydro fluorocarbons (HFCs) are being phasedout due to their ozone depletion potential (ODP) and global warmingpotential (GWP).

Furthermore, closed-cell foams derived from polystyrene and polyurethanethat can have a thermal conductivity of less than 0.03 W/m·K are highlyflammable and thus have limited application as building insulationmaterial even with the addition of flame retardants. Foams derived frompolyisocyanurates exhibit better flame resistance than polystyrene andpolyurethane, and phenolic foams exhibit even better flame resistancethan polyisocyanurate foams. However, phenolic foams use a phenol basedmonomer which is produced from a petroleum feedstock, a depletingnon-renewable resource and formaldehyde as another monomer, which isclassified as human carcinogenic.

Link et al., BioResources, 6(4), 4218-4228, disclose synthesis offormaldehyde-free tannin-based foams using mimosa tannin and furfurylalcohol in an acid environment applying a temperature between 120° C.and 160° C.

Hence, there is a need for low thermal conductivity and fire resistantpolymeric foams free of formaldehyde and made from renewable sourceshaving a closed-cell structure with trapped blowing agent preferablywith low ODP and low GDP.

SUMMARY OF THE INVENTION

In an aspect of the invention, there is a foam comprising:

-   -   (a) a continuous polymeric phase defining a plurality of cells,        wherein:        -   the continuous polymeric phase comprises a tannin-based            resin derived from a tannin, and a monomer, the monomer            comprising furfural, glyoxal, acetaldehyde,            5-hydroxymethylfurfural, acrolein, levulinate esters,            sugars, 2,5-furandicarboxylic acid, 2,5-furandicarboxylic            aldehyde, urea, difurfural (DFF), furfuryl alcohol,            glycerol, sorbitol, lignin, or mixtures thereof,        -   the plurality of cells comprises a plurality of open-cells            and a plurality of closed-cells with an open-cell content            measured according to ASTM D6226-5, of less than 50%; and    -   (b) a discontinuous phase disposed in at least a portion of the        plurality of closed-cells, the discontinuous phase comprising        one or more blowing agents.        In another aspect of the invention, there is a process        comprising:

(a) forming an agglomerate-free solution comprising:

-   -   10-80% by weight of a tannin,    -   5-80% by weight of a monomer, the monomer comprising furfural,        glyoxal, acetaldehyde, 5-hydroxymethylfurfural, acrolein,        levulinate esters, sugars, 2,5-furandicarboxylic acid,        2,5-furandicarboxylic aldehyde, urea, difurfural (DFF), furfuryl        alcohol, glycerol, sorbitol, lignin, or mixtures thereof, and    -   5-30% by weight of water,

(b) mixing 1-30% by weight of one or more blowing agents with theagglomerate-free solution to form a pre-foam mixture; and

(c) mixing 5-30% by weight of an acid catalyst with the pre-foam mixtureto form a foam composition,

wherein 0.5-10% by weight of a surfactant is added to at least one ofthe steps (a), (b), or (c), and

wherein the amounts in % by weight are based on the total weight of theagglomerate-free solution;

(d) processing the foam composition to form a foam.

The foregoing general description and the following detailed descriptionare exemplary and explanatory only and are not restrictive of theinvention, as defined in the appended claims.

DETAILED DESCRIPTION

Disclosed is a foam comprising a continuous polymeric phase defining aplurality of cells, wherein the continuous polymeric phase comprises atannin-based resin derived from a tannin and a monomer, and wherein theplurality of cells comprises a plurality of open-cells and a pluralityof closed-cells. The foam also comprises a discontinuous phase disposedin at least a portion of the plurality of closed-cells, thediscontinuous phase comprising one or more blowing agents.

As used herein, the term “open-cell” refers to individual cells that areruptured or open or interconnected producing a porous “sponge” foam,where the gas phase can move around from cell to cell. As used herein,the term “closed-cell” refers to individual cells that are discrete,i.e. each closed-cell is enclosed by polymeric sidewalls that minimizethe flow of a gas phase from cell to cell. It should be noted that thegas phase may be dissolved in the polymer phase besides being trappedinside the closed-cell. Furthermore, the gas composition of theclosed-cell foam at the moment of manufacture does not necessarilycorrespond to the equilibrium gas composition after aging or sustaineduse. Thus, the gas in a closed-cell foam frequently exhibitscompositional changes as the foam ages leading to such known phenomenonas increase in thermal conductivity or loss of insulation value.

In one embodiment, the foam has an open-cell content of less than 50% orless than 40%, or less than 30%, as measured according to ASTM D6226-5.In another embodiment, the foam has an open-cell content of less than20% or less than 10%, as measured according to ASTM D6226-5.

In an embodiment, the continuous polymeric phase of the foam comprises atannin-based resin derived from a tannin and a monomer present in aweight ratio in the range of 1:0.005 to 1:4 or 1:0.01 to 1:2.

In an embodiment, the tannin used in the foam comprises bio-derivedtannin. As used herein, bio-derived tannins are vegetable-based,extracted from leaf, bud, seed, root, bark, trunk, nut shells, skins offruits, and stem tissues of plants and trees. Exemplary bio-derivedtannins include, but are not limited to, mimosa, acacia, quebracho,pine, spruce, fir, tanoak, oak, birch, maple, eucalyptus, tare, catechu,or mixtures thereof. As used herein, the term “mimosa tannin” refers toa tannin extracted from leaf, bud, seed, root, bark, trunk, or stemtissues of a mimosa tree; and so on. In an embodiment, the continuouspolymeric phase of the foam comprises a tannin-based resin derived froma monomer and a tannin comprising at least one of a mimosa tannin or aquebracho tannin, or a spruce tannin. In another embodiment, the tanninused in the foam comprises synthetic tannin. Synthetic tannins are alsoknown as syntans. Exemplary syntans include, but are not limited to,sulfonated phenol-formaldehyde resins, sulfonated melamine-formaldehyderesin, sulfonated naphtalene-formaldehyde resins. In another embodiment,the tannin is a mixture of bio-derived tannin and syntan.

A suitable monomer is selected from furfural, glyoxal, acetaldehyde,5-hydroxymethylfurfural, acrolein, levulinate esters, sugars,2,5-furandicarboxylic acid, 2,5-furandicarboxylic aldehyde, urea,difurfural (DFF), furfuryl alcohol, glycerol, sorbitol, lignin, ormixtures thereof. Other suitable biomass derived monomers are disclosedin “Liquid Phase catalytic Processing of Biomass-derived OxygenatedHydrocarbons to fuels and Chemicals”, by Chheda et. al. in AngewandteChemie, Int., 2007, 46, 7164-7183, the disclosure of which isincorporated by reference herein in its entirety.

In one embodiment, the continuous polymeric phase of the foam comprisesa formaldehyde-free tannin-based resin derived from a tannin andfurfuryl alcohol. In another embodiment, the continuous polymeric phaseof the foam comprises a formaldehyde-free tannin-based resin derivedfrom a tannin, furfuryl alcohol, and furfural. As used herein, the term“formaldehyde-free tannin-based resin” means that the tannin-based resinis formed without the use of formaldehyde as a monomer.

As used herein, the term “blowing agent” is used interchangeably withthe term “foam expansion agent”. In general, the blowing agent must bevolatile and inert, and can be inorganic or organic. In an embodiment,at least one of the one or more blowing agents has a gas phase thermalconductivity of less than or equal to 0.016 W/m·K or less than or equalto 0.014 W/m·K or less than or equal to 0.012 W/m·K at 25° C. In anembodiment, at least one of the one or more blowing agents present inthe foam comprises 1,1,1,4,4,4-hexafluoro-2-butene available as FEA-1100from E.I. du Pont de Nemours and Company (Wilmington, Del.). In anotherembodiment, at least one of the one or more blowing agents present inthe foam comprises carbon dioxide; hydrocarbons such as pentane,isopentane, cyclopentane petroleum ether, and ether;hydrochlorofluorocarbons such as 1,1-dichloro-1-fluoroethane(HCFC-141b); 2,2-dichloro-1,1,1-trifluoroethane (HCFC-123);1-chloro-1,1-difluoroethane (HCFC-142b); 1,1,1,2-tetrafluoroethane(HCFC-134a); 1,1,1,3,3-pentafluoropropane (HFC-245fa) available fromHoneywell (Morristown, N.J.); 1,1,1,3,3-pentafluorobutane (HFC-365)available as Solkane® 365mfc from Solvay Chemicals (Bruxelles, Belgium);incompletely halogenated hydrocarbons such as 2-chloropropane;fluorocarbons such as dichlorodifluoromethane,1,2-dichloro-1,1,2,2-tetrafluoroethane (CFC-114),trichlorotrifluoroethane (CFC-113), trichloromonofluoromethane (CFC-11),or mixtures thereof.

As used herein, ozone depletion potential (ODP) of a chemical compoundis the relative amount of degradation to the ozone layer it can cause,with trichlorofluoromethane (CFC-11) being fixed at an ODP of 1.0. Asused herein, the global-warming potential (GWP) used herein is arelative measure of how much heat a greenhouse gas traps in theatmosphere. It compares the amount of heat trapped by a certain mass ofthe gas in question to the amount heat trapped by a similar mass ofcarbon dioxide, which is fixed at 1 for all time horizons (20 years, 100years, and 500 years). For example, CFC-11 has GWP (100 years) of 4750.Hence, from the global warming perspective, a blowing agent should havezero ODP and as low GWP as possible.

In some embodiments, at least one of the one or more blowing agents hasan ozone depletion potential (ODP) of less than 2, or less than 1 or 0.In other embodiments, at least one of the one or more blowing agents hasa global warming potential (GWP) of less than 5000, or less than 1000,or less than 500. An exemplary blowing agent with zero ODP and a low GWPis 1,1,1,4,4,4-hexafluoro-2-butene (ODP=0 and GWP=5).

In one embodiment, the foam has a density in the range of 10-500 kg/m³,or 20-100 kg/m³, or 20-80 kg/m³.

In another embodiment, the foam has a thermal conductivity in the rangeof 0.015-0.05 W/m·K, or 0.015-0.04 W/m·K, or 0.015-0.03 W/m·K. Theoverall conductivity of the foam is strongly determined by the thermalconductivity of the gas phase or the discontinuous phase and theopen-cell content of the foam. This is because the gas phase or thediscontinuous phase disposed in at least a portion of the plurality ofthe closed-cells in a low-density foam (having a density in the range of20-80 kg/m³), usually makes up about 95% of the total foam volume.Hence, only those foams that are blown from low thermal conductivityblowing agents and result in closed cell structures, with significantfraction of the blowing agent trapped within the closed cells, canexhibit thermal conductivity lower than that of air. For example, if theopen-cell content of a low density foam is more than 90%, then the foamwill constitute mostly air, which exhibits a thermal conductivity in therange of 0.025-0.026 W/m·K at room temperature. Thus, a predominantlyopen-cell foam (with an open-cell content of more than 90%) will exhibita thermal conductivity that is greater than 0.025 W/m·K. Similarly, apredominantly closed-cell foam (with closed-cell content of more than90%) will have a thermal conductivity determined by the gas phasethermal conductivity of the blowing agent. For foams with anintermediate level (20-80%) of open cell and/or closed cell content, thethermal conductivity of the foam will be determined by the volumefraction and the thermal conductivity of the blowing agent.

For several different applications where thermal insulation is required,it is desirable that the insulation material exhibit low flammability.Flammability of a material may be evaluated by several different methodsknown to those skilled in the art. One method is to measure the LimitingOxygen Index (LOI), which represents the concentration of oxygenrequired to sustain a flame during the burning of a material (ASTM2863). The higher the LOI of a material the lower is its flammability.Thus it is desirable that insulating foams exhibit as high a LOI aspossible. In an embodiment, the disclosed foam has a limiting oxygenindex (LOI) of at least 23, or at least 25, or at least 30.

In addition to the closed cell content, the size of the cells in a foamcan also affect the resulting thermal conductivity. In addition tothermal properties, the cell size of the foam can also affect otherproperties of the foam, such as but not limited to the mechanicalproperties. In general, it is desirable that the cells of the foam besmall and uniform. However, the size of the cells cannot be reducedindefinitely because for a given density foam if the cell size becomestoo small the thickness of the cell walls can become exceedingly thinand hence can become weak and rupture during the blowing process orduring use. Hence, there is an optimum size for the cells depending onthe density of the foam and its use. In one embodiment, a cell, eitheran open-cell or a closed-cell, has an average size of less than 500microns. In another embodiment, the cell has an average size of lessthan 300 microns and in yet another embodiment the cell has an averagesize of less than 200 microns. Cell size may be measured by differentmethods known to those skilled in the art of evaluating porousmaterials. In one method, thin sections of the foam can be cut andsubjected to optical or electron microscopic measurement, such as usinga Hitachi S2100 Scanning Electron Microscope available from Hitachiinstruments (Schaumburg, Ill.).

In an embodiment, the continuous polymer phase further comprises one ormore surfactants, with at least one of ionic or non-ionic surfactants,including polymeric surfactants. A class of suitable surfactantsincludes siloxane-oxyalkylene copolymers such as those containing Si—O—Cas well as Si—C linkages. The siloxane-oxyalkylene copolymers can beblock copolymers or random copolymers. Typical siloxane-oxyalkylenecopolymers contain a siloxane moiety composed of recurringdimethylsiloxy units endblocked with mononethylsiloxy and/ortrimethylsiloxy units and at least one polyoxyalkylene chain composed ofoxyethylene and/or oxypropylene units capped with an organic group suchas an ethyl group. Suitable siloxane-oxyalkylene copolymeric surfactantsinclude, but are not limited to, polyether-modified polysiloxanes,available as Tegostab B8406 from Evonik Goldschmidt Corporation(Hopewell, Va.); (polyalkyleneoxide modified heptamethyltrisiloxaneavailable as Silwet L-77 from OSi Specialties (Danbury Conn.).

Another class of suitable surfactants includes silicone surfactants suchas, L-7003, L-5350, L-5420, and L-5340 silicone surfactants, allavailable from Union Carbide Corporation, DC 193 available from DowChemical Co. (Midland, Mich.), and SF™1188 silicone surfactant availablefrom GE Bayer Silicones.

Another class of suitable surfactants includes non-ionic organicsurfactants such as the condensation products of alkylene oxides such asethylene oxide, propylene oxide or mixtures thereof, and alkylphenolssuch as nonylphenol, dodecylphenol, and the like. Suitable non-ionicorganic surfactants include, but are not limited to, polysorbate(Tween®) surfactant, for example Tween® 20, Tween® 21, Tween® 61, Tween®80 or Tween® 81 all available from Aldrich Chemical Company; Pluronic®non-ionic surfactants available from BASF Corp., (Florham Park, N.J.);Tergitol™; Brij® 98, Brij® 30, and Triton X 100, all available fromAldrich Chemical Company; and Merpol®LF available from E.I. du Pont deNemours and Company (Wilmington Del.). Suitable ionic surfactantincludes, but is not limited to sodium dodecylsulfonate (SDS).

In other embodiment, the continuous polymer phase further comprises oneor more acid catalysts. Suitable acid catalysts include, but are notlimited to, benzenesulfonic acid, para-toluenesulfonic acid,xylenesulfonic acid, naphthalenesulfonic acid, ethylbenzenesulfonicacid, phenolsulfonic acid, sulfuric acid, phosphoric acid, boric acid,hydrochloric acid or mixtures thereof.

In another embodiment, the continuous polymer phase further comprisesone or more additives. Suitable additives include, but are not limitedto, cellulose fiber, bacterial cellulose, sisal fiber, clays,Kaolin-type clay, mica, vermiculite, sepiolite, hydrotalcite and otherinorganic platelet materials, glass fibers, polymeric fibers, aluminafibers, aluminosilicate fibers, carbon fibers, carbon nanofibers,poly-1,3-glucan, lyocel fibers, chitosan, boehmite (AlO.OH), zirconiumoxide, or mixtures thereof. The additive can also be a plasticizercomprising a polyester polyol, formed by the reaction of a polybasiccarboxylic acid with a polyhydridic alcohol selected from a dihydridicto a pentahydridic. Examples of the acid include but are not limited toadipic acid, sebacic acid, naphthalene-2,6-dicarboxylic acid,cyclohexane-1,3-dicarboxylic acid, phthalic acid. Examples of thepolyhydric alcohol include but are not limited to ethylene glycol,propylene diol, propylene glycol, 1,6-hexane diol, 1,4-butane diol and1,5-pentane diol. In an embodiment, the plasticizer is polyester polyol.The average molecular weight is in the range of 100-50,000 g/mol, or200-40,000 g/mol, or 200-1000 g/mol.

In one embodiment, the tannin-based foam is disposed between two similaror dissimilar non-foam materials, also called facers to form a sandwichpanel structure. Any suitable material can be used for the facers. Inone embodiment, the facers may be formed from a metal such as, but notlimited to aluminum and stainless steel. In another embodiment, thefacers may be formed from plywood, cardboard, composite board, orientedstrand board, gypsum board, fiber glass board, and other buildingmaterials known to those skilled in the art. In another embodiment, thefacers may be formed from nonwoven materials derived from glass fibersand/or polymeric fibers such as Tyvek® and Typar® available from E.I.DuPont de Nemours & Company. In another embodiment, the facers may beformed from woven materials such as canvas and other fabrics. Yet, inanother embodiment, the facers may be formed of polymeric films orsheets. Exemplary polymers for the facer may include, but are notlimited to, polyethylene, polypropylene, polyesters, and polyamides.

The disclosed tannin-based foams are bio-derived, low density rigidfoams, having low thermal conductivity and low flammability. Thedisclosed tannin foams could be used for a variety of applications,including, but not limited to, thermal insulation of building envelopes,and household and industrial appliances. Furthermore, the disclosedfoams can also be used in combination with other materials such assilica aerogels as a support for the fragile aerogel, and potentially asa catalyst support. Additional advantages of the disclosed foamsinclude, but are not limited to, the use of less toxic materials, zeroformaldehyde emission, improved flame resistance, mold resistance,enhanced biodegradability, and micro-organism resistance.

In accordance with the present invention, there is provided a process ofmaking a tannin-based foam. The process comprises forming anagglomerate-free solution comprising a tannin, a monomer, and water.

The tannin used in the tannin-phenolic foam may be bio-derived tannin,syntan, or a mixture thereof. Suitable bio-derived tannin comprisesmimosa, acacia, quebracho, pine, spruce, fir, tanoak, oak, birch, maple,eucalyptus, tara, catechu, or mixtures thereof. In an embodiment, thetannin is dried. The tannin may be dried at a temperature in the rangeof 50-200° C., or 80-150° C., or 90-120° C. for an amount of time in therange of 1-7 days, or 1-5 days, or 1-3 days before the step of mixingthe tannin with a monomer, and water. In another embodiment, the tanninis used as is. The amount of dried tannin is in the range of 10-99.9%,or 50-99%, or 80-98%, by weight, based on the total weight of theagglomerate-free solution.

Suitable monomer comprises furfural, glyoxal, acetaldehyde,5-hydroxymethylfurfural, acrolein, levulinate esters, sugars,2,5-furandicarboxylic acid, 2,5-furandicarboxylic aldehyde, urea,difurfural (DFF), furfuryl alcohol, glycerol, sorbitol, lignin, ormixtures thereof. The amount of the monomer present in the mixture is inthe range of 5-80%, or 10-70%, or 15-50%, by weight, based on the totalweight of the agglomerate-free solution.

Other suitable biomass derived monomers are disclosed in “Liquid Phasecatalytic Processing of Biomass-derived Oxygenated Hydrocarbons to fuelsand Chemicals”, by Chheda et. al. in Angewandte Chemie, Int., 2007, 46,7164-7183, the disclosure of which is incorporated by reference hereinin its entirety.

The step of forming an agglomerate-free solution comprises mixing atannin with a monomer, and water to form a mixture and providing aresidence time to the mixture to effectively dissolve the tannin in themixture. At the start of the residence time, the mixture may compriseagglomerates of tannin, wherein one may observe a two phase system withone phase being agglomerates of tannin and the other phase being liquidcomprising dissolved tannin in a monomer, and water. As the agglomeratesof tannin dissolves, the mixture becomes more viscous. At the end of theresidence time, the mixture is a one phase system comprising dissolvedtannin in a monomer, and water. The step of providing a residence timemay involve keeping the mixture still for the residence time, or mixingthe mixture for a certain amount of time, or mixing and keeping stillfor the rest of the residence time.

Any suitable method can be used to mix a tannin with a monomer, andwater, to form an agglomerate-free solution, such as, for example, handmixing, mechanical mixing using a Kitchen-aid® mixer, a twin screwextruder, a bra-blender, an overhead stirrer, a ball mill, an attritionmill, a Waring blender, or a combination thereof.

In an embodiment, the step of forming an agglomerate-free solutioncomprising a tannin, a monomer, and water can include first mixing thetannin with water and then adding the monomer to the mixture of tanninand water. In other embodiment, the step of forming an agglomerate-freesolution comprising a tannin, a monomer, and water can include firstmixing the tannin with the monomer and then adding water to the mixtureof tannin and monomer. In another embodiment, the step of forming anagglomerate-free solution comprising a tannin, a monomer, and water caninclude first mixing the monomer with water and then adding tannin tothe mixture of monomer and water.

When the tannin is first mixed with a monomer and/or water, it may forma two phase system with one phase comprising agglomerates of tannin andthe second phase comprising dissolved tannin in the monomer and water.However, after a certain amount of residence time, the two phase systemwill become a single phase system, i.e., an agglomerate-free solutioncomprising dissolved tannin, the monomer, and water. The amount ofresidence time needed to obtain an agglomerate-free solution will dependon the temperature at which the tannin is mixed with a monomer, andwater and also on the composition and the extent of mixing.

The process of making a tannin-based foam also comprises mixing one ormore blowing agents with the agglomerate-free solution to form apre-foam mixture. In an embodiment, at least one of the one or moreblowing agents has a gas phase thermal conductivity of less than orequal to 0.016 W/m·K or less than or equal to 0.014 W/m·K or less thanor equal to 0.012 W/m·K at 25° C. In other embodiment, at least one ofthe one or more blowing agents is 1,1,1,4,4,4-hexafluoro-2-buteneavailable as FEA-1100 from E.I. du Pont de Nemours and Company(Wilmington, Del.). Suitable blowing agents include, but are not limitedto carbon dioxide; hydrocarbons such as pentane, isopentane,cyclopentane petroleum ether, and ether; hydrochlorofluorocarbons suchas 1,1-dichloro-1-fluoroethane (HCFC-141b);2,2-dichloro-1,1,1,2-trifluoroethane (HCFC-123);1-chloro-1,1-difluoroethane (HCFC-142b); 1,1,1,2-tetrafluoroethane(HCFC-134a); 1,1,1,3,3-pentafluoropropane (HFC-245fa) available fromHoneywell (Morristown, N.J.); 1,1,1,3,3-pentafluorobutane (HFC-365)available as Solkane® 365mfc from Solvay Chemicals (Bruxelles, Belgium);incompletely halogenated hydrocarbons such as 2-chloropropane;fluorocarbons such as dichlorodifluoromethane,1,2-dichloro-1,1,2,2-tetrafluoroethane (CFC-114),trichlorotrifluoroethane (CFC-113), trichloromonofluoromethane (CFC-11),or mixtures thereof. The amount of blowing agent is in the range of1-30%, or 1-20%, or 1-10%, by weight, based on the total weight of theagglomerate-free solution.

The process of making a tannin-based foam further comprises mixing5-30%, or 10-25%, or 10-20%, by weight of an acid catalyst with thepre-foam mixture to form a foam composition, based on the total weightof the agglomerate-free solution. In an embodiment, the acid catalystcomprises benzenesulfonic acid, para-toluenesulfonic acid,xylenesulfonic acid, naphthalenesulfonic acid, ethylbenzenesulfonicacid, phenolsulfonic acid, sulfuric acid, phosphoric acid, boric acid,hydrochloric acid or mixtures thereof. In another embodiment, the acidcatalyst comprises para-toluenesulphonic acid and xylenesulphonic acidin a weight ratio in the range of 0.67:1 to 9:1, or 2:1 to 7:1, or 3:1to 5:1. In other embodiment, the acid catalyst is dissolved in a minimumamount of solvent, the solvent comprising ethylene glycol, propyleneglycol, dipropylene glycol, butyrolactone, dimethyl sulfoxide,N-methyl-2-pyrrolidone, morpholines, propane diol, or mixtures thereof.A catalyst is normally required to produce the foam but in some cases, afoam can be made without a catalyst but rather using thermal aging. Acombination of thermal aging and a catalyst is commonly used. In somecases, the reaction is exothermic and hence little or no additional heatmay be required.

In an embodiment, a small amount of catalyst, between 5-40% or 5-20%, byweight of the total amount of the acid to be added maybe added to thetannin during the step of forming an agglomerate-free solution andthereby allowing some pre-reaction prior to foaming for an amount oftime in the range of 5 min to 24 h.

The process of making a tannin-based foam also comprises processing thefoam composition to form a foam comprising a continuous polymeric phasedefining a plurality of cells, and a discontinuous phase comprising theone or more blowing agents disposed in at least a portion of theplurality of cells. The step of processing the foam compositioncomprises maintaining the foam composition at an optimum temperature. Inan embodiment, the optimum temperature is in the range of 25-100° C., or35-90° C., or 45-85° C. In another embodiment, the step of processingthe foam composition comprises foaming the foam composition in asubstantially closed mold. In one embodiment, the foam composition isfirst foamed at an optimum temperature in the range of 25-100° C., or35-90° C., or 45-85° C. in an open mold and then the mold is closed andkept at that temperature for an amount of time in the range of 25-100°C., or 35-90° C., or 45-85° C. As used herein, the term “closed mold”means partially closed mold where some gas may escape, or completelyclosed mold, where the system is sealed. In some cases, the foam isformed in a closed mold or under application of pressure to control thefoam density. Pressures from atmospheric to up to 5000 kPa may beapplied depending upon the desired foam density.

In one embodiment, the process of making a tannin-based foam comprisesadding a surfactant to the agglomerate-free solution. In anotherembodiment, a surfactant is added to the pre-foam mixture. Thesurfactant is first mixed with the blowing agent and then the mixture ofblowing agent and surfactant is mixed with the agglomerate-free solutionto form a pre-foam mixture. In another embodiment, a surfactant is mixedwith the acid catalyst. The amount of surfactant present in at least oneof the agglomerate-free solution, the pre-foam mixture, or the foamcomposition is in the range of 0.5-10%, or 2-8%, or 3-6%, by weight,based on the total weight of the agglomerate-free solution.

The surfactant is present in an effective amount to emulsify theagglomerate-free solution, the blowing agent, the catalyst and optionaladditives of the foam composition. The surfactant is added to lower thesurface tension and stabilize the foam cells during foaming and curing.The surfactant is at least one of ionic or non-ionic surfactants,including polymeric surfactants. A class of suitable surfactantsincludes siloxane-oxyalkylene copolymers such as those containing Si—O—Cas well as Si—C linkages. The siloxane-oxyalkylene copolymers can beblock copolymers or random copolymers. Typical siloxane-oxyalkylenecopolymers contain a siloxane moiety composed of recurringdimethylsiloxy units endblocked with mononethylsiloxy and/ortrimethylsiloxy units and at least one polyoxyalkylene chain composed ofoxyethylene and/or oxypropylene units capped with an organic group suchas an ethyl group. Suitable siloxane-oxyalkylene copolymeric surfactantsinclude, but are not limited to, polyether-modified polysiloxanes,available as Tegostab B8406 from Evonik Goldschmidt Corporation(Hopewell, Va.); (polyalkyleneoxide modified heptamethyltrisiloxaneavailable as Silwet L-77 from OSi Specialties (Danbury Conn.).

Another class of suitable surfactants includes silicone surfactants suchas, L-7003, L-5350, L-5420, and L-5340 silicone surfactants, allavailable from Union Carbide Corporation, DC 193 available from DowChemical Co. (Midland, Mich.), and SF™ 1188 silicone surfactantavailable from GE Bayer Silicones.

Another class of suitable surfactants includes non-ionic organicsurfactants such as the condensation products of alkylene oxides such asethylene oxide, propylene oxide or mixtures thereof, and alkylphenolssuch as nonylphenol, dodecylphenol and the like. Suitable non-ionicorganic surfactants include, but are not limited to, polysorbate(Tween®) surfactant, for example Tween® 20, Tween® 21, Tween® 61, Tween®80 or Tween® 81 all available from Aldrich Chemical Company; Pluronic®non-ionic surfactants available from BASF Corp., (Florham Park, N.J.);Tergito™; Brij® 98, Brij® 30, and Triton X 100, all available fromAldrich Chemical Company; and Merpol®LF available from E.I. du Pont deNemours and Company (Wilmington Del.). Suitable ionic surfactantincludes, but is not limited to sodium dodecylsulfonate (SDS).

In an embodiment, the process of making a tannin-based foam furthercomprises adding an additive to at least one of the agglomerate-freesolution or the pre-foam mixture. The amount of additive is in the rangeof 5-50%, or 10-45%, or 15-40%, by weight based on the total weight ofthe agglomerate-free solution. Suitable additives include, but are notlimited to, cellulose fiber, bacterial cellulose, sisal fiber, clays,Kaolin-type clay, mica, vermiculite, sepiolite, hydrotalcite and otherinorganic platelet materials, glass fibers, polymeric fibers, aluminafibers, aluminosilicate fibers, carbon fibers, carbon nanofibers,poly-1,3-glucan, lyocel fibers, chitosan, boehmite (AlO.OH), zirconiumoxide, or mixtures thereof. The additive can also be a plasticizercomprising a polyester polyol, formed by the reaction of a polybasiccarboxylic acid with a polyhydridic alcohol selected from a dihydridicto a pentahydridic. Examples of the acid include but are not limited toadipic acid, sebacic acid, naphthalene-2,6-dicarboxylic acid,cyclohexane-1,3-dicarboxylic acid, phthalic acid. Examples of thepolyhydric alcohol include but are not limited too ethylene glycol,propylene diol, propylene glycol, 1,6-hexane diol, 1,4-butane diol and1,5-pentane diol. In an embodiment, the plasticizer is polyester polyol.The average molecular weight is in the range of 100-50,000 g/mol, or200-40,000 g/mol, or 200-1000 g/mol.

In one embodiment, the process of making a tannin-based foam furthercomprises disposing a tannin-based foam between two similar ordissimilar non-foam materials, also called facers to form a sandwichpanel structure. Any suitable material can be used for the facers. Inone embodiment, the facers may be formed from a metal such as, but notlimited to aluminum and stainless steel. In another embodiment, thefacers may be formed from plywood, cardboard, composite board, orientedstrand board, gypsum board, fiber glass board, and other buildingmaterials known to those skilled in the art. In another embodiment, thefacers may be formed from nonwoven materials derived from glass fibersand/or polymeric fibers such as Tyvek® and Typar® available from E.I.DuPont de Nemours & Company. In another embodiment, the facers may beformed from woven materials such as canvas and other fabrics. Yet, inanother embodiment, the facers may be formed of polymeric films orsheets. Exemplary polymers for the facer include, but are not limitedto, polyethylene, polypropylene, polyesters, and polyamides.

The thickness of the facer material would vary depending on theapplication of the sandwich panel. In some cases, the thickness of thefacer material could be significantly smaller than the thickness of thefoam while in other cases the thickness of the facer material could becomparable or even greater than the thickness of the sandwiched foam.

In some embodiments, the facer material may be physically or chemicallybonded to the tannin-based foam to increase the structural integrity ofthe sandwich panel. Any suitable method can be used for physical meansof bonding including, but not limited to, surface roughening bymechanical means and etching by chemical means. Any suitable method canbe used for chemical bonding including, but not limited to, use ofcoatings, primers, and adhesion promoters that form a tie layer betweenthe facer surface and the foam.

As used herein, the terms “comprises,” “comprising,” “includes,”“including,” “has,” “having” or any other variation thereof, areintended to cover a non-exclusive inclusion. For example, a process,method, article, or apparatus that comprises a list of elements is notnecessarily limited to only those elements but may include otherelements not expressly listed or inherent to such process, method,article, or apparatus. Further, unless expressly stated to the contrary,“or” refers to an inclusive or and not to an exclusive or. For example,a condition A or B is satisfied by any one of the following: A is true(or present) and B is false (or not present), A is false (or notpresent) and B is true (or present), and both A and B are true (orpresent).

As used herein, the phrase “one or more” is intended to cover anon-exclusive inclusion. For example, one or more of A, B, and C impliesany one of the following: A alone, B alone, C alone, a combination of Aand B, a combination of B and C, a combination of A and C, or acombination of A, B, and C.

Also, use of “a” or “an” are employed to describe elements and describedherein. This is done merely for convenience and to give a general senseof the scope of the invention. This description should be read toinclude one or at least one and the singular also includes the pluralunless it is obvious that it is meant otherwise.

Unless otherwise defined, all technical and scientific terms used hereinhave the same meaning as commonly understood by one of ordinary skill inthe art to which this invention belongs. Although methods and materialssimilar or equivalent to those described herein can be used in thepractice or testing of embodiments of the disclosed compositions,suitable methods and materials are described below. All publications,patent applications, patents, and other references mentioned herein areincorporated by reference in their entirety, unless a particular passageis cited. In case of conflict, the present specification, includingdefinitions, will control. In addition, the materials, methods, andexamples are illustrative only and not intended to be limiting.

In the foregoing specification, the concepts have been disclosed withreference to specific embodiments. However, one of ordinary skill in theart appreciates that various modifications and changes can be madewithout departing from the scope of the invention as set forth in theclaims below.

Benefits, other advantages, and solutions to problems have beendescribed above with regard to specific embodiments. However, thebenefits, advantages, solutions to problems, and any feature(s) that maycause any benefit, advantage, or solution to occur or become morepronounced are not to be construed as a critical, required, or essentialfeature of any or all embodiments.

It is to be appreciated that certain features are, for clarity,described herein in the context of separate embodiments, may also beprovided in combination in a single embodiment. Conversely, variousfeatures that are, for brevity, described in the context of a singleembodiment, may also be provided separately or in any subcombination.Further, reference to values stated in ranges include each and everyvalue within that range.

The concepts disclosed herein will be further described in the followingexamples, which do not limit the scope of the invention described in theclaims.

The examples cited here relate to tannin-based foams. The discussionbelow describes how a tannin-based foam without use of formaldehyde isformed.

EXAMPLES Test Methods

Density Measurement

Apparent density (ρ) of the foams was measured by a) cutting a foam intoa regular shape such as a rectangular cube or cylinder, b) measuring thedimensions and the weight of the foam piece, c) evaluating the volume ofthe foam piece and then dividing the weight of the foam piece by thevolume of the foam piece.

More specifically, three cylindrical pieces were cut from a test foamusing a brass corer having an internal diameter of 1.651 mm (0.065′) tocalculate the average apparent density of the test foam. The diameterand the length of the cylindrical pieces were measured using Vemiercalipers and then the volume (V) of the cylinder was calculated. Themass (m) of each cylindrical piece was measured and used to calculatethe apparent density (ρ_(a)) of each foam piece.

$\rho_{a} = \frac{m}{V}$Open-Cell Content

Open-cell content of foams was determined using ASTM standard D6226-5.All measurements were made at room temperature of 24° C.

Pycnometer density (ρ) of each cylindrical piece was measured using agas pycnometer, Model # Accupyc 1330 (Micromeritics InstrumentCorporation, Georgia, U.S.A) at room temperature using nitrogen gas.

The AccuPyc works by measuring the amount of displaced gas. Acylindrical foam piece was placed in the pycnometer chamber and bymeasuring the pressures upon filling the chamber with a test gas anddischarging it into a second empty chamber, volume (V_(s)) of thecylindrical foam piece that was not accessible to the test gas wascalculated. This measurement was repeated five times for each foamcylindrical piece and the average value for V_(s) was calculated.

The volume fraction of open-cells (O_(v)) in a foam sample wascalculated by the following formula:

$O_{v} = \frac{( {V - V_{s}} )}{V}$

Assuming the specific gravity of the solid tannin polymer to be 1 g/cm³,the volume fraction of the cell walls (CW_(v)) was calculated from thefollowing formula:

${CW}_{v} = \frac{m}{V}$

Thus the volume fraction of closed cells (C_(v)) was estimated by thefollowing equation:C _(v)=1−O _(v) −CW _(v)Thermal Conductivity

Hot Disk Model #PPS 2500S (Hot Disk AB, Gothenberg, Sweden) was used tomeasure thermal conductivities of the foams.

A foam whose thermal conductivity needed to be measured was cut into tworectangular or circular test pieces of same size. The lateral dimensionsand the thickness of the foam pieces were required to be greater thanfour times the radius of the Hot Disk heater and sensor coil. The radiusof the heater and sensor coil for all measurements was 6.4 mm and hencethe lateral dimensions and the thickness of the foam pieces were greaterthan 26 mm.

Before the start of a measurement protocol, the heater and sensor coilwas sandwiched between two test pieces of foam and the entire assemblywas clamped together to ensure intimate contact between the surfaces ofthe foam pieces and the heater and sensor coil.

At the start of a test, a known current and voltage was applied to theheater and sensor coil. As the heater and sensor coil heated up due tothe passage of current through the coil, the energy was dissipated tothe surrounding test pieces of foam. At regular time intervals duringthe experiment, the resistance of the heater and sensor coil was alsomeasured using a precise wheat stone bridge built into the Hot Diskapparatus. The resistance was used to estimate the instantaneoustemperature of the coil. The temperature history of the heater andsensor coil was then used to calculate the thermal conductivity of thefoam using mathematical analysis presented in detail by Yi He inThermochimica Acta 436, pp 122-129, 2005.

The test pieces of foam were allowed to cool and the thermalconductivity measurement on the test pieces was repeated two more times.The thermal conductivity data was then used to calculate the averagethermal conductivity of the foam.

Starting Materials

As used in the Examples below, mimosa tannin was purchased fromSilvaTeam (Italy). Furfuryl alcohol and furfural were purchased fromSigma-Aldrich (St. Louis, Mo.). Surfactants, Tegostab B8406(polyether-modified polysiloxane) was purchased from Evonik GoldschmidtCorporation (Hopewell, Va.) and DC 193 was purchased from Dow ChemicalCo. (Midland, Mich.). Acid catalysts p-toluenesulfonic acid andxylenesulfonic acid were purchased from Sigma-Aldrich (St. Louis, Mo.).Blowing agents pentane was purchased from Sigma-Aldrich (St. Louis, Mo.)and FEA-1100 (1,1,1,4,4,4-hexafluoro-2-butene) was purchased from E.I.du Pont de Nemours and Company (Wilmington, Del.).

Example 1: Preparation of Formaldehyde-Free Tannin-Based Foam (FFTF-1)with FEA-1100

Mimosa tannin was dried at 100° C. for 2 days before use. Furfurylalcohol (8 g), water (6 g), and a surfactant Tegostab B8406 (1 g) wasmixed and added to mimosa tannin (20 g). The mixture was stirred with aspatula three times and left at room temperature for 3 h. The abovemixture (10 g) was removed and FEA-1100 (2 g) was mixed into the mixtureuntil a stable weight was achieved. Next p-toluenesulfonicacid/xylenesulfonic acid (1.25 g, a 70/30 mixture dissolved in a minimumamount of ethylene glycol) was added and mixed for 2 min. The materialwas then transferred to a 250 mL polypropylene bottle and placed in anoven at 60° C. with the cap off. After 4.5 min, the cap was placed onthe bottle and the bottle along with its contents was left in the ovenat 60° C. After 3 days, the cap was removed, and the bottle was leftuncapped at 50° C. for an additional 1 day to remove any volatiles. Theas-prepared formaldehyde-free tannin-based foam, FFTF-1 had an open cellof 12.7% and an apparent density of 0.05 g/cc. The thermal conductivityof the foam, FFTF-1 was measured to be 0.025 W/m·K.

Example 2: Preparation of Formaldehyde-Free Tannin-Based Foam (FFTF-2)with Pentane

Mimosa tannin was dried at 100° C. for 2 days before use. Furfurylalcohol (40 g), water (30 g), and a surfactant Tegostab B840 (5 g) wasmixed and added to mimosa tannin (100 g). The mixture was stirred with aspatula three times and left at room temperature for 12-18 h. A portion(20 g) of the above mixture was removed and a pentane (1.5 g) was mixedinto the mixture until a stable weight was achieved. Nextp-toluenesulfonic acid/xylenesulfonic acid (3 g, a 70/30 mixturedissolved in a minimum amount of ethylene glycol) was added and mixedfor 2 min. The material was then transferred to a 500 mL polypropylenebottle and placed in a water bath at 50° C. with the cap off. After 5min, the cap was placed on the bottle and the bottle along with itscontents was placed in an oven at 50° C. for 12-18 h. The cap was thenremoved, and the bottle was left uncapped at 50° C. for an additional 1day to remove any volatiles. The as-prepared formaldehyde-freetannin-based foam. FFTF-2 had an open cell of 6.24% and an apparentdensity of 0.036 g/cc. The thermal conductivity of the foam, FFTF-2 wasmeasured to be 0.026 W/m·K.

Example 3: Preparation of Formaldehyde-Free Tannin-Based Foam (FFTF-3)with Pentane

Mimosa tannin was dried at 100° C. for 2 days before use. Furfurylalcohol (4 g), furfural (4 g), water (6 g), and a surfactant DC 193 (1g) was mixed and added to mimosa tannin (10 g). The mixture was stirredwith a spatula three times and left at room temperature for 4 h. Aportion (10 g) of the above mixture was removed and a foam expansionagent (1.5 g of pentane) was mixed into the mixture until a stableweight was achieved. Next p-toluenesulfonic acid/xylenesulfonic acid(1.25 g, a 70/30 mixture dissolved in a minimum amount of ethyleneglycol) was added and mixed for 3 min. The material was then transferredto a 250 mL polypropylene bottle and placed in a water bath at 50° C.with the cap off. After 10 min in the water bath, the cap was placed onthe bottle and the bottle along with its contents was placed in an ovenat 50° C. After 3 days, the cap was removed, and the bottle was leftuncapped at 50° C. for an additional 1 day to remove any volatiles. Theas-prepared formaldehyde-free tannin-based foam, FFTF-3 had an open cellof 6.37% and an apparent density of 0.045 g/cc. The thermal conductivityof the foam, FFTF-3 was measured to be 0.026 W/m·K.

Example 4: Preparation of Formaldehyde-Free Tannin-Based Foam (FFTF-4)with Pentane

Mimosa tannin was dried at 100° C. for 2 days before use. Furfurylalcohol (4 g), furfural (4 g), water (6 g), and Tegostab B8406 (1 g) wasmixed and added to the mimosa tannin (10 g). The mixture was stirredwith a spatula three times and left at room temperature for 4 h. Aportion (15 g) of the above mixture was removed and pentane (1 g) wasmixed into the mixture until a stable weight was achieved. Nextp-toluenesulfonic acid/xylenesulfonic acid (1.8 g, a 70/30 mixturedissolved in a minimum amount of ethylene glycol) was added and mixedfor 3 min. The material was then transferred to a 250 mL polypropylenebottle and placed in a water bath at 50° C. with the cap off. After 10min in the water bath, the cap was placed on the bottle and the bottlealong with contents was placed in an oven at 50° C. After 3 days, thecap was removed, and the bottle was left for an additional 1 day at 50°C., to remove any volatiles. The as-prepared formaldehyde-freetannin-based foam, FFTF-4 had an open cell of 9.8% and an apparentdensity of 0.049 g/cc. The thermal conductivity of the foam, FFTF-4 wasmeasured to be 0.027 W/m·K.

Example 5: Preparation of Formaldehyde-Free Tannin-Based Foam (FFTF-5)with FEA-1100

Mimosa tannin was dried at 100° C. for 2 days before use. Furfurylalcohol (8 g), water (6 g), and a surfactant (1 g, Evonik TegostabB8406) was mixed and added to mimosa tannin (20 g). The mixture wasstirred with a spatula three times and left at room temperature for 3 h.A portion (14.68 g) of the above mixture was removed and a foamexpansion agent (3.9 g, FEA-1100, DuPont, Wilmington, Del.) was mixedinto the mixture until a stable weight was achieved. Nextp-toluenesulfonic acid/xylenesulfonic acid (2 g, a 70/30 mixturedissolved in a minimum amount of ethylene glycol) was added and mixedfor 2 min. The material was then transferred to a 250 mL polypropylenebottle and placed in an oven at 50° C. with the cap off. After 4.5 minin the oven, the cap was placed on the bottle and the bottle along withits contents was left in the oven at 50° C. After 3 days, the cap wasremoved, and the bottle was left at 50° C. for an additional 1 day toremove any volatiles. The as-prepared formaldehyde-free tannin-basedfoam, FFTF-5 had an open cell of 34.52% and an apparent density of 0.088g/cc. The thermal conductivity of the foam, FFTF-5 was measured to be0.036 W/m·K.

Example 6: Preparation of Formaldehyde-Free Tannin-Based Foam (FFTF-6)with FEA-1100

Example 3 was repeated with the exception that after the 4 h mixing, aportion (10 g) of the above mixture was removed and FEA-1100 (1.8 g) wasmixed into the mixture until a stable weight was achieved, followed byaddition of p-toluenesulfonic acid/xylenesulfonic acid (2.4 g, a 70/30mixture dissolved in a minimum amount of ethylene glycol). The foamingprocedure as described in the Example 1 was used. The as-preparedformaldehyde-free tannin-based foam, FFTF-6 had an open cell of 10% andan apparent density of 0.05 g/cc. The thermal conductivity of the foam,FFTF-6 was measured to be 0.025 W/m·K.

Example 7: Preparation of Formaldehyde-Free Tannin-Based Foam (FFTF-7)with FEA-1100

Mimosa tannin was dried at 100° C. for 2 days before use. Furfurylalcohol (2 g), furfural (2 g), water (3 g), and a surfactant DC-193 (0.5g) was mixed and added to the mimosa tannin (10 g). The mixture wasstirred with a spatula three times and left at room temperature for 2 h.FEA-1100 (3 g) was mixed into the above mixture until a stable weightwas achieved. Next p-toluenesulfonic acid/xylenesulfonic acid (1.87 g, a70/30 mixture dissolved in a minimum amount of ethylene glycol) wasadded and mixed for 3 min. The material was then transferred to a 250 mLpolypropylene bottle and placed in an oven at 50° C. with the cap off.After 8 min in the oven, the cap was placed on the bottle and the bottlealong with contents was left the oven at 50° C. After 3 days, the capwas removed and the bottle was left at 50° C. for an additional 1 day toremove any volatiles. The as-prepared formaldehyde-free tannin-basedfoam, FFTF-7 had an open cell of 15% and an apparent density of 0.054g/cc. The thermal conductivity of the foam, FFTF-7 was measured to be0.028 W/m·K.

Example 8: Preparation of Formaldehyde-Free Tannin-Based Foam (FFTF-8)with FEA-1100

Example 7 was repeated with the exception that 10 g of the mixture oftannin, furfural alcohol, furfural, water, and surfactant was mixed withFEA-1100 (2 g). Next p-toluenesulfonic acid/xylenesulfonic acid (1.25 g,a 70/30 mixture dissolved in a minimum amount of ethylene glycol) wasadded and mixed for 3 min. The foaming procedure as described in theExample 4 was used. The as-prepared formaldehyde-free tannin-based foam,FFTF-8 had an open cell of 6.89% and an apparent density of 0.05 g/cc.The thermal conductivity of the foam, FFTF-8 was measured to be 0.026W/m·K.

Example 9: Preparation of Formaldehyde-Free Tannin-Based Foam (FFTF-9)with FEA-1100

Example 7 was repeated with the exception that the foaming temperaturewas 60° C. The as-prepared formaldehyde-free tannin-based foam, FFTF-9had an open cell of 6.89% and an apparent density of 0.042 g/cc. Thethermal conductivity of the foam, FFTF-9 was measured to be 0.025 W/m·K.

Example 10: Preparation of Formaldehyde-Free Tannin-Based (FFTF-10) Foamwith FEA-1100

Example 7 was repeated with the exception that p-toluenesulfonicacid/xylenesulfonic acid (0.25 g, a 70/30 mixture dissolved in a minimumamount of ethylene glycol) was added to the mixture comprising furfurylalcohol, furfural, water, surfactant and tannin and the mixture left for12-18 h. FEA-1100 (2 g) was mixed into the above mixture until a stableweight was achieved. Next p-toluenesulfonic acid/xylenesulfonic acid (1g, a 70/30 mixture dissolved in a minimum amount of ethylene glycol) wasadded and mixed for 3 min. The foaming procedure as described in theExample 4 was used with the exception that the bottle was not capped,i.e. an open system. The as-prepared formaldehyde-free tannin-basedfoam, FFTF-10 had an open cell of 7% and an apparent density of 0.058g/cc. The thermal conductivity of the foam. FFTF-10 was measured to be0.025 W/m·K.

Example 11: Preparation of Formaldehyde-Free White Spruce Tannin-BasedFoam (FFTF-11) with Pentane

White spruce tannin was extracted from the bark of a North AmericanSpruce tree by boiling the bark (1 Kg) in water at 95° C. for 2 h. Theas-prepared brown solution was filtered and dried, with an yield ofwhite spruce tannin of 16 wt %. Next, the white spruce tannin (50 g) wasadded to furfuryl alcohol (38 g) and water (12 g) in a beaker, and themixture was gently heated on a hot plate to 60° C. for 2 h. A portion(24 g) of the mixture containing the white spruce tannin was thenfurther concentrated by heating in a beaker at 75° C. for 1 h to a finalweight of 21.5 g. To a portion (18 g) of the concentrated mixture, asurfactant Tegostab B8406 (1.45 g) was added, followed by the additionof pentane (3.75 g) along with stirring until a constant weight of 3.75g was achieved. Next, p-toluenesulfonic acid/xylenesulfonic acid (3.8 g,a 70/30 mixture dissolved in a minimum amount of ethylene glycol) wasadded and mixed for 2 min. The material was then transferred to a 500 mLpolypropylene bottle and placed in an oven at 60° C. with the cap off.After 1 min, the cap was placed on the bottle and the bottle along withits contents was left in the oven at 60° C. After 4 h, the cap wasremoved, and the bottle was left uncapped at 50° C. for an additional 1day to remove any volatiles. The as-prepared formaldehyde-free whitespruce tannin-based foam, FFTF-11 had an open cell of 45% and anapparent density of 0.0258 g/cc.

In the foregoing specification, the invention has been described withreference to specific embodiments. However, one of ordinary skill in theart appreciates that various modifications and changes can be madewithout departing from the scope of the invention as set forth in theclaims below. Accordingly, the specification and figures are to beregarded in an illustrative rather than a restrictive sense and all suchmodifications are intended to be included within the scope of invention.

Benefits, other advantages, and solutions to problems have beendescribed above with regard to specific embodiments. However, thebenefits, advantages, solutions to problems, and any element(s) that maycause any benefit, advantage, or solution to occur or become morepronounced are not to be construed as a critical, required, or essentialfeature or element of any or all the claims.

What is claimed is:
 1. A foam consisting of: (a) a continuous polymericphase defining a plurality of cells, wherein: the continuous polymericphase consists of a formaldehyde-free tannin-based resin derived from atannin, furfuryl alcohol and an optional monomer excluding formaldehyde,the monomer comprising furfural, glyoxal, acetaldehyde,5-hydroxymethylfurfural, acrolein, levulinate esters, sugars,2,5-furandicarboxylic acid, 2,5-furandicarboxylic aldehyde, urea,difurfural (DFF), glycerol, sorbitol, lignin, or mixtures thereof, theplurality of cells comprises a plurality of open-cells and a pluralityof closed-cells with an open-cell content measured according to ASTMD2856, of less than 40%; and (b) a gas phase comprising one or moreblowing agents disposed in at least a portion of the plurality ofclosed-cells.
 2. The foam of claim 1, wherein the tannin and furfurylalcohol are present in a weight ratio in the range of 1:0.1 to 1:2. 3.The foam of claim 1, wherein the open-cell content measured according toASTM D2856, is less than 20%.
 4. The foam of claim 1, wherein theopen-cell content measured according to ASTM D2856, is less than 30%. 5.The foam of claim 1, wherein the foam has a density in the range of10-500 kg/m³.
 6. The foam of claim 1, wherein the foam has a density inthe range of 20-100 kg/m³.
 7. The foam of claim 1, wherein at least oneof the one or more blowing agents has a gas phase thermal conductivityof less than or equal to 0.016 W/m·K at 25° C.
 8. The foam of claim 1,wherein at least one of the one or more blowing agents comprises1,1,1,4,4,4-hexafluoro-2-butene, carbon dioxide, pentane, isopentane,cyclopentane petroleum ether, ether, 1,1-dichloro-1-fluoroethane,2,2-dichloro-1,1,1-trifluoroethane, 1-chloro-1,1-difluoroethane,1,1,1,2-tetrafluoroethane, 1,1,1,3,3-pentafluoropropane,1,1,1,3,3-pentafluorobutane, 2-chloropropane, dichlorodifluoromethane,1,2-dichloro-1,1,2,2-tetrafluoroethane, trichlorotrifluoroethane,trichloromonofluoromethane, or mixtures thereof.
 9. The foam of claim 1,wherein the foam has a thermal conductivity in the range of 0.015-0.050W/m·K.
 10. The foam of claim 1, wherein the continuous polymeric phasefurther comprises one or more surfactants.
 11. The foam of claim 1,wherein the tannin is derived from mimosa, acacia, quebracho, pine,spruce, fir, tanoak, oak, birch, maple, eucalyptus, tara, catechu, ormixtures thereof.
 12. The foam of claim 1, wherein the foam has alimiting oxygen index of at least 23, measured according to ASTM-D2863.13. An article comprising the foam of claim
 1. 14. The article of claim13 comprising a sandwich panel structure, wherein the sandwich panelstructure comprises the foam disposed between two similar or dissimilarnon-foam materials.
 15. The article of claim 14 wherein the non-foammaterial comprises polymeric fibers.
 16. The foam of claim 1, whereinthe continuous polymeric phase further comprises one or more additives.17. The foam of claim 16, wherein the one or more additives comprisescellulose fiber, bacterial cellulose, sisal fiber, clays, Kaolin-typeclay, mica, vermiculite, sepiolite, hydrotalcite and other inorganicplatelet materials, glass fibers, polymeric fibers, alumina fibers,aluminosilicate fibers, carbon fibers, carbon nanofibers,poly-1,3-glucan, lyocel fibers, chitosan, boehmite (AIO.OH), zirconiumoxide, a polyester polyol, or mixtures thereof.